The present invention relates to a method and a device for identifying the fuel quality in a fuel tank of an internal combustion engine, in particular of an internal combustion engine of a motor vehicle.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Methods for identifying the fuel quality in a fuel tank of an internal combustion engine are advantageous in particular with so-called flex-fuel vehicles, which can be operated selectively with gasoline or with ethanol, which have quite different combustion and calorific values. In addition, such methods are also used with motor vehicles having a diesel engine, because these can also be operated with fuels having a different combustion or cetane values. To achieve optimal combustion, the fuel quality must always be considered when controlling the mixture, for example by changing the injected fuel quantity. This process is typically referred to as adaption.
With adaption, it is determined after the startup of the internal combustion engine based, for example, on a deviation of a parameter of the combustion, for example a deviation of the fuel-air ratio measured with a sensor, detected when evaluating a signal from a lambda probe, if the combustion takes place according to specification, or if deviations occur. In the latter case, the motor controller performs an adaptation by controlling the mixture to again provide optimal combustion conditions.
Although deviations from a specification can be determined by evaluating the signal from a lambda probe, these deviations may have different causes, so that a measured deviation can not always be easily correlated with a specific cause, for example a change in the fuel quality. For example, leakage in the region of the injection system or in the air system may cause a similar deviation of the signal of the lambda probe as refilling the fuel tank with a fuel having a lower calorific value.
In addition to evaluating the signal from a lambda probe, other methods exist for determining the quality of the fuel in a fuel tank of an internal combustion engine of a motor vehicle during operation of the motor vehicle. However, most of these methods also cause problems in that a deviation of a measured parameter which is evaluated for identifying the fuel quality may also have other causes, so that a change in the fuel quality cannot be inferred with certainty from the deviation of the parameter.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method and an improved device which enables a reliable determination if a deviation of a measured parameter evaluated for identifying the fuel quality is caused by a change in the fuel quality or is due to other causes.